What is a shell voicing?


Jim, 
A shell voicing is a chord which contains only the root, third, and seventh.
 Often players will only use two notes, the root and third.  

The formulas for the basic minor 7th, dominant 7th, and major 7th chords all
include a perfect 5th,  which makes it a non-factor in identifying the
differences between these three chords.  For this reason, and possibly the
fact that the root (either included in the voicing or played by the bassist)
generates the perfect 5th as one of its strongest overtones, it is often
excluded from voicings.
 

The pianist Bill Evans often used these "third and seventh only" chords in
his left hand comps.  Many guitar players (Emily Remler, Jim Hall, John
Stowell, John Abercrombie, Mike Stern, Alan DeMause, etc.) use shell voicings
in solo, duo, and trio situations where they want to add the harmonies "like
a pianist" behind their melodies or solos.  Joe Pass (among others) used the
R,3,and 7 form often to make walking bass lines combined with chordal comps.

I hope this helped you! 

Brian Oates